This invention relates to turbomachinery blades and, more particularly, to an improved tip cap configuration for such a blade.
It is well known that gas turbine engine efficiency is, at least in part, dependent upon the extent to which compressed air in the compressor or expanding combustion products in the turbine leak across a gap between blading members and opposing surfaces, such as shrouds. In the hotter turbine section, the problem of interference between such cooperating members is more critical because of greater differences in their thermal expansion or contraction characteristics. Therefore, a variety of configurations for tip caps for the type of hollow turbine blades used in modern gas turbine engines has been reported. Typical of such configurations are those described in U.S. Pat. Nos. 3,854,842; 3,899,267 and 4,010,531, issued Dec. 17, 1974, Aug. 12, 1975 and Mar. 8, 1977, respectively. The disclosure of each of such patents is incorporated herein by reference.
During operation of a gas turbine engine, interference between such relatively rotating blade tips and opposing surfaces, due to differences in coefficients of thermal expansion, has resulted in worn or damaged blade tips. Because of the complexity and relative high cost of such a component, it is desirable to repair rather than to replace such an article.